Side firing optical fiber device for consistent, rapid vaporization of tissue and extended longevity

ABSTRACT

A side firing laser device suitable for use in medical and surgical procedures has a laser energy transmission efficiency in excess of 90% and provides consistent and rapid vaporization of tissue as well as long useful life. The device includes a conduit with an optical fiber therewithin. The optical fiber is adapted for coupling to a laser energy source at the proximal end thereof and has a beveled distal end portion capped by a closed end capillary tube which, in turn, is surrounded by a reflective sheath with a side port through which laser energy emitted by the optical fiber can pass.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/706,517, filed on Sep. 27, 2012, which is incorporated herein byreference in its entirety.

FIELD OF INVENTION

This invention relates to improved fiber optic laser energy deliverydevices.

BACKGROUND OF THE INVENTION

Commercially available glass optical fibers efficiently transmit lightat various wavelengths. Such glass optical fibers typically have a fusedsilica core, sometimes also referred to as a quartz, core, surrounded bya cladding of fused silica doped with materials to lower its refractiveindex to a level lower than that of the core, an optional polymercladding with a lower refractive index than that of the glass cladding,which increases the effective numerical aperture of the optical fiber,and a buffer coating that protects the optical fiber from mechanicaldamage.

For efficient transmission of wavelengths of about 190 nm to 1100 nm,the core of the optical fiber must have a high hydroxyl ion content,known as a “High-OH Fiber” (a hydroxyl ion content of about 600 to 1000ppm), and the glass cladding would typically, but may not, also have aHigh-OH content.

For efficient transmission of wavelengths from about 500 nm to 2300 nm,some of which wavelengths of light (between 1400 nm to 1500 nm andbetween 1800 nm to 2300 nm) are highly absorbed by water, the core ofthe optical fiber must have a low hydroxyl ion content, known as a“Low-OH Fiber” (hydroxyl ion content of about 0.1 to 100 ppm), and theglass cladding would typically, but may not, also have a Low-OH content.

When used in medical procedures, such glass optical fibers typicallyhave a core to cladding ratio of about 1:1.1 to 1:1.2. Drawing customfibers with either larger core to cladding ratios can entail specialproduction runs, delays in delivery and possibly substantial additionalcost.

To allow such an optical fiber to deliver light substantially laterallyto the longitudinal axis of the optical fiber, the buffer coating andany polymer cladding may be removed from the distal end portion of theoptical fiber, hereinafter referred to “baring” or a “bared” opticalfiber, the core and cladding of the optical fiber may be beveled at anangle of about 33° to 45°, and the bared portion of the optical fibermay be disposed within in a distally closed-ended capillary tube.Commonly, the capillary tube is fixed in place over the bared, beveled,distal end portion of the optical fiber by fusing the capillary tube tothe bared portion of the optical fiber at a high temperature.Alternatively, the capillary tube may be attached to the optical fiberby the use of an adhesive, a combination of thermal fusing and anadhesive or other means known in the art. The capillary tube creates anair environment opposite the distal, beveled end surface of the opticalfiber.

Laser energy or power transmitted through such a side firing opticalfiber device, hereinafter referred to as a “side firing fiber” or “sidefiring device”, is emitted laterally from the axis of the optical fiberby total internal reflection, which requires fluid interface with anindex of refraction significantly lower than the index of refraction ofthe core of the optical fiber, such as air, opposite the beveled distalend surface of the optical fiber. According to Snell's law, within knownlimitations, laser energy or power will be emitted from such an opticalfiber device at an angle double the angle of the beveled, distal end ofthe optical fiber.

Directing light laterally from the axis of a side firing fiber is usefulin many medical applications, including high laser energy or powerapplications such as vaporizing a portion of the lobes of an enlargedprostate that is obstructing urine flow, a condition called benignprostatic hyperplasia or “BPH”, or vaporizing a portion of the nucleuspulposa of a herniated spinal disc, to relieve the pressure of the discon nerves in the spine, which causes pain, vaporizing a solid tumor andother applications.

Conventional side firing devices suffer from several light transmissionefficiency losses, including but not limited to at least one of thefollowing: (a) many of the higher order light modes impinging on thebeveled, distal end surface of the optical fiber at angles higher thanthose which allow total internal reflection, causing a portion of thetransmitted light to be emitted in directions other than the primarilyintended direction; (b) aberrant reflections of light arising from thebeveled, distal end surface of the optical fiber which, even if verycarefully beveled and polished, may not be absolutely flat; (c) aberrantreflections of light arising from the interface between the interiorsurface of the capillary tube and the outer surface of the bared opticalfiber; (d) diminished transparency of the capillary tube due to damageto and erosion of the capillary tube from various sources; (e) aberrantreflections of light arising from the capillary tube acting as awaveguide and transmitting light forward and backward along thelongitudinal axis of the optical fiber; (f) aberrant emissions of lightfrom damage to the thin, beveled distal edge or end surface of theoptical fiber from light reflected back from the target tissue, (g)substantial tip vibration due to each pulse of light energy of awavelength highly absorbed by water, such as from wavelengths of laserenergy at 1400 to 1500 nm and 1800 to 2300 nm, which cause the almostinstant conversion of water in the cells of the target tissue and anyaqueous irrigation liquid to a steam bubble, whose expansion oppositethe capillary tube disposed over the beveled, distal end surface of theoptical fiber causes an equal and opposite force to be exerted againstthe capillary tube and the distal end of the side firing device, whichcan cause small or fatal cracks in the optical fiber and/or thecapillary tube; (h) small cracks in the optical fiber and/or capillarytube created or expanded by the shock wave resulting from the collapseof the steam bubbles described in (g) above; (i) high levels of residualstress in the capillary tube caused by rapid thermal gradients whenclosing the distal end of the capillary tubing or fusing the capillarytubing to the glass cladding of the optical fiber, as it cools; and (j)softening and loss of flatness and/or integrity of the beveled distalend surface of the optical fiber due to thermal diffusion during fusionof the capillary tube to the glass cladding of the optical fiber.

Diminished transparency of the capillary tube can occur due to damage toand erosion of the capillary tube from various sources, including butnot limited to laser energy reflected back from the target tissue,called “back reflected laser energy”, degradation of the capillary tubefrom tissue, blood and other bodily fluids back-splattered from thevaporization of tissue, which absorb laser energy and degrade thecapillary tube, called “back splatter degradation”, reducing its laserenergy transmission efficiency, and exposure of the capillary tube tohot gasses from the vaporization of tissue and, at wavelengths of laserenergy which are highly absorbed by water, vaporization of the aqueousirrigation liquid commonly used in endoscopic procedures, causingerosion of the capillary tube, a process called “hydrothermal erosion”.If the capillary tube becomes sufficiently eroded or fractures, the airinterface opposite the distal beveled end surface of the optical fibermay be lost, in which case the light will essentially be emittedstraight ahead. In medical applications, this could cause unintendeddamage to a blood vessel, nerve or other tissue.

Lasers that emit wavelengths between about 190 nm to 1100 nm include forexample, excited dimer or “excimer” lasers emitting at 193, 222, 248,308 or 351 nm. Lasers emitting between about 400 to 1800 nm include, forexample, argon lasers emitting at 488 to 514 nm, KTP lasers emitting at532 nm, Nd:YAG lasers emitting at 1,064 nm, diode lasers emitting atvarious wavelengths from about 500 nm to 1800 nm, and a number ofothers. Lasers emitting at 1800-2300 nm include Thulium:YAG lasersemitting at 2000 nm and CTH:YAG lasers emitting at 2100 nm, generallycalled “Holmium” lasers, and others.

Diode and KTP lasers, emitting at least 80 watts of power, are able tovaporize tissue, albeit with some adverse effects, including charring(which prompts a healing response, causing pain and irritation for a fewweeks), and inadvertent coagulation of deeper, unseen tissues, due tothe light penetration and thermal diffusion to depths of 3 to 4 mm ormore for these wavelengths in tissue, causing edema or swelling, whichcan take weeks to subside. When these lasers are used to vaporize aportion of the lobes of the prostate gland to treat BPH, residualcoagulated tissue sloughs-off in the urine over a few weeks, causingpain and irritation for some weeks, and may cause periodic bleeding asthe coagulated, dead tissue separates from live tissue.

As a result of the above adverse effects, pulsed lasers which emit inthe 1800 to 2300 nm wavelength range, whose energy is highly absorbed bywater, a constituent of virtually all living cells, have beeneffectively used for more efficient vaporization of tissue. Such lasersinclude typically emit laser energy in pulses with a duration of about150 to 800 microseconds, typically at a pulse repetition rate of about 5to 60 pulses per second, or alternately CW or quasi-CW, depending uponthe application.

The light extinction or penetration depth of Holmium laser energy at awavelength of 2100 nm is only about 0.4 mm in most tissues and theirrigation liquid cools the tissue between pulses, resulting in littleor no charring and little thermal diffusion in tissue, resulting in lessedema and swelling, and eliminating the inadvertent coagulation of ordamage to unseen, deeper tissues. The steam bubbles created byvaporization of the irrigation liquid, when they cool, return to watervapor and ultimately to their liquid state.

For example, at a pulse repetition rate of 40 Hertz and a pulse width of350 microseconds, there are 24,650 microseconds between each 350microsecond pulse, for the irrigation liquid to cool the tissue betweenpulses, resulting in little or no charring of tissue.

Steam bubbles are almost instantly created upon each pulse of Holmiumlaser energy in an aqueous liquid field, like an explosion, as describedbriefly in subparagraph (g) above. As the steam bubbles expand, theycause an equal and opposite force to be exerted on the distal, laserenergy emitting end of the bared optical fiber and capillary tubeassembly, causing rapid movement, which can cause minute cracks to formand expand in the capillary tube, the distal end portion of the baredoptical fiber and in the optical fiber near the optical fiber's fulcrumpoint.

When the steam bubbles collapse, they cause acoustic shocks, as brieflydescribed in subparagraph (h) above, which can cause fractures in thecapillary tube and the distal end portion of the bared optical fiber,diminishing their transmission efficiency. These acoustic shocks and theinstant creation of steam bubbles occur with pulsed lasers from 5 to 50or more times per second, resulting in rapid movement or vibration ofthe distal end of the side firing device. If such vibration causes thecapillary tube or optical fiber to form cracks or break, light willescape in an aberrant direction, may damage unintended tissues and couldharm the patient, operator or bystanders.

Commercially available side firing devices typically have an initiallight transmission efficiency of only about 70 to 90%, which efficiencyrapidly declines during use at higher laser powers (for example, at 50Watts and above), and such side firing devices usually have thecapability to vaporize only about 20 to 60 grams of soft tissue, such asthe tissue of the male prostate gland, before failing or reaching anunacceptably low vaporization rate, which requires the side firingdevice to be discarded.

When designing a side firing device for medical applications, theoutside diameter (“OD”) of a given device, consisting of the opticalfiber, its attached capillary tube, and any optional outer tip or sheathshould generally not exceed about 2.0 to 2.35 mm. If the distal end ofthe side firing device is optionally encased in a hollow, open-endedplastic or metal sheath, which protects the capillary tube from backsplatter degradation and mechanical damage, with an opening or port foremission of the laser energy disposed 180° opposite the beveled, distalend surface of the optical fiber, the overall OD of the side firingdevice should generally not exceed about 2.0 to 2.3 mm. This isimportant, as endoscopes presently used in many surgical suitestypically have an instrument channel with an inside diameter (“ID”) of2.5 to 2.667 mm (7.5 to 8.0 French). While endoscopes with largerinstrument channels are presently being marketed, physicians andhospitals prefer using their current inventory of endoscopes withsmaller ODs, which are able to enter and pass through the urethra in thepenis without damage to the urethra or to reach other tissues throughsmall incisions or natural orifices.

A low core to glass cladding ratio of the optical fiber is generallyless expensive and enables a thicker capillary tube to be used, whosegreater thickness reduces the potential for damage from laser energyback reflected from the target tissue, back splatter degradation andhydrothermal erosion of the capillary tube, which can cause itspremature failure, as described above. However, using a low core tocladding ratio subjects the thin, leading edge of the beveled, distalend surface of the optical fiber to damage, such as during assembly,transport and use, as described above, significantly reducing thetransmission efficiency of the side firing device.

For example, a typical, commercially available 550 micron core diameteroptical fiber, after the removal of its protective buffer coating andany polymer cladding from its distal end portion, has a core to claddingratio of 1:1.1 and an O.D. of 600 microns, enabling a capillary tubewith a wall thickness of about 500 microns to be disposed over thedistal end portion of the optical fiber, bringing the O.D. of thecombination to about 1650 microns or 1.65 mm. If an optional, hollow,protective plastic or metal sheath is used to encase the capillary tube,with a port for emission of laser energy as described above, with a wallthickness of about 300 microns, and allowing for a gap of 25 micronsbetween the sheath and the capillary tube, the O.D. of the assembly willbe about 2,300 microns or 2.30 mm.

Commercially available side firing fibers made by Lumenis, Ltd. (YokneamIndustrial Park, Israel) are used with Holmium lasers at a wavelength of2100 nm, and commercially available side firing devices made by AmericanMedical Systems Holdings, Inc. (Minnetonka, Minn.) are used with KTPlasers at a wavelength of 532 nm. Both of their side firing fibers haveinitial laser energy transmission efficiencies of about 75% to 90%,which decline relatively rapidly over time during their use, and aregenerally able to vaporize, at 100 or 120 watts of power, respectively,only about 20 to 60 grams of soft tissue, such as that of the maleprostate gland, before declining in tissue vaporization efficiency tounacceptable levels or failing. These devices employ core to claddingratios of about 1:1.1 and 1:1.4 or larger, respectively.

In many cases, reduced tissue vaporization rates during usage andfailure of such side firing fibers from the loss of total internalreflection occurs. When this happens, laser light transmission must beimmediately ceased by the surgeon to avoid damage to an unintendedtissue, the failed device must be removed from the patient anddiscarded, and a new side firing fiber must be obtained from sterilestorage, brought to the operating room, unpackaged, positioned in thepatient and used to finish the treatment, substantially increasing thecost and time of the procedure.

It is an object of this invention to provide a side firing device whichhas a consistent, high laser energy transmission efficiency over 90%,with sufficient functional longevity (durability) and high reliabilityto enable it to efficiently and rapidly vaporize at least 90 grams ofsoft tissue prior to failure, such as the tissue of the male prostategland, at a manufacturing cost as low as possible. Indeed, since singleuse, side firing devices sell for about $600 to $900 in the UnitedStates, if such a side firing device was sufficiently durable tovaporize at least 90 grams of soft tissue, it may be able to be cleaned,re-sterilized and used to remove sufficient tissue to treat, perhaps,three 30 to 50 gram prostates and, perhaps, two 60 to 90 gram prostates,significantly reducing the cost of the procedure.

SUMMARY OF THE INVENTION

A side firing laser device suitable for use in medical and surgicalprocedures provides consistent, rapid vaporization of tissue andextended longevity. The device has a laser energy transmissionefficiency in excess of 90%.

The side firing laser device includes an elongated conduit within whichis situated an optical fiber with a beveled distal end capped by aclosed end capillary tube carried by the conduit. The capillary tube issurrounded with an internally reflective sheath that defines a portthrough which laser energy emitted by the optical fiber exits.

In particular, the conduit has an open distal end to which is mounted acapillary tube that defines a cavity therewithin. The cavity ispositioned to be in communication with the open end of the conduit. Anoptical fiber, adapted for coupling to a laser energy source, isprovided in the conduit and terminates in a beveled distal end portionwhich freely extends into the cavity. The capillary tube is surroundedby a bulbous or rounded, internally reflective metal sheath which isalso mounted to the conduit and which defines a port from which laserenergy emitted by the beveled distal end portion of the optical fibercan exit. The sheath also defines an aperture which is aligned with theoptical axis of the optical fiber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external, top view of a source of laser energy and a sidefiring optical fiber device constructed in accordance with the presentinvention.

FIG. 2 is a partial, cross-sectional, side view of the distal endportion of a side firing optical fiber device constructed in accordancewith the present invention.

FIG. 3 is a partial, cross-sectional, side view of the proximal endportion of the shaft, handle, and other components utilized with a sidefiring optical fiber device constructed in accordance with the presentinvention.

FIG. 4 is a cross-sectional, end view at plane 4-4 in FIG. 2 of the sidefiring optical fiber device of FIG. 2.

FIG. 5 is a cross-sectional, end view at plane similar to 4-4 in FIG. 2of a more preferred embodiment of the side firing optical fiber deviceof the present invention.

FIG. 6 is a partial side image of the distal end portion of a sidefiring optical fiber device constructed in accordance with the presentinvention, prior to use.

FIG. 7 is a partial side image of the distal end portion of a sidefiring optical fiber device constructed in accordance with the presentinvention, after 90 minutes of use.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While this invention is susceptible of embodiment in many differentforms, there are shown in the drawings and will be described in detailherein specific embodiments thereof, with the understanding that thepresent disclosure is to be considered as an exemplification of theprinciples of the invention and is not to be limited to the specificembodiments illustrated.

To achieve the above mentioned objects of this invention and efficientlytransmit at least 80 watts or more of laser power at, for example, awavelength of 2100 nm from a Holmium laser, the components of the sidefiring device must be composed of and constructed to incrementally andconsistently increase the laser energy transmission efficiency of thedevice, increase the rapidity and consistency of its tissuevaporization, extend its functional longevity, provide high reliabilityand provide optimal handling and positioning of the device.

These can be achieved by a series of features, entailing at least oneof: (a) an optimal OD of the core of the optical fiber, allowing it toefficiently accept and transmit the amount and wavelength of laserenergy desired, while being sufficiently small to allow the use of acladding and thicker walled capillary tube; (b) an optimal wallthickness and composition of the glass cladding surrounding the core ofthe optical fiber, to minimize the size and cost of the cladding, whichis typically the most expensive part of a glass optical fiber, (c) anoptimal wall thickness of glass tubing collapsed over the glasscladding, to prevent excessive dispersion and damage to the thin leadingedge of the beveled, distal end surface of the optical fiber during use;(d) an optimal OD of the bared optical fiber, which is sufficientlysmall to enable as large as possible wall thickness of a distallyclosed-ended capillary tube to be used to encase the beveled, distal endportion of the bared optical fiber; (e) an optimal bevel angle of thedistal end surface of the optical fiber polished with a beveled angleslightly higher than would normally be predicted for total internalreflection (or “TIR”) given the numerical aperture and dispersion of theoptical fiber materials using normal equations as known in the art, toreduce the transmission loss from the side firing optical fiber deviceby directing a higher percentage of the incoming laser energy laterallyfrom its longitudinal axis; (f) an optimal flatness of the beveled,distal end surface of the optical fiber, to reduce losses which wouldreduce the side firing device's transmission efficiency; (g) an optimalthickness of the closed-ended capillary tube disposed over the beveled,distal end portion of the bared optical fiber, to maximize the device'sfunctional longevity by increasing the capillary tube's resistance todamage and minimizing its susceptibility to hydrothermal erosion; (h) anoptimal manner of attachment of the distally closed-ended capillary tubedisposed over the beveled, distal end portion of the bared opticalfiber, to maximize the side firing device's functional longevity byincreasing the capillary tube's resistance to damage from back reflectedlaser energy, back splatter degradation and hydrothermal erosion duringuse; (i) an optimal means of fabricating the closed-ended capillary tubeto optimize performance with respect to residual stresses remaining thecapillary tube material(s) from thermally closing its distal end bythermal fusing and its cooling; (j) an optimal straightness andpositioning of the bared distal end portion of the optical fiber toresist its being damaged during assembly with the capillary tube andduring use; (k) an optimal protective sheath over the capillary tubewith a port for emission of laser energy, to enable the capillary tubeto resist the formation and/or propagation of minute cracks within thecapillary tube from back reflection of laser energy, back splatterdegradation and hydrothermal erosion, as described above; (l) an optimalprotective sheath being fully or partially composed of a material highlyreflective to the wavelength of laser energy being used, to reducedistal end losses by reflecting a higher percentage of both aberrantemissions within the device and reflected energy from the target tissueaway from the longitudinal axis of the optical fiber, (m) an optimalhollow, relatively rigid shaft disposed over the optical fiber, proximalto the capillary tube, to enable the side firing device to resist therapid movement or vibration resulting from the equal and opposite forcesexerted on the distal end portion of the side firing device from theformation of steam bubbles and acoustic shocks occurring 5 to 50 timesor more a second, as described above; (n) an optimal protective,lubricious plastic sleeve or coating disposed over the shaft encasingthe optical fiber to allow the side firing device to be easily insertedinto, used within and withdrawn from the working channel of commonlyavailable endoscopes, without damage to the sleeve; (o) an optimal meansto relieve pressure from the expansion of air or gasses trapped betweenthe beveled, distal end surface of the optical fiber and the capillarytube, which are heated during lasing, to allow any gas pressuredifferential that may develop during use to be equalized; (p) an optimalmeans to fix the optical fiber in place, with respect to the capillarytube, to reduce stresses on the optical fiber during insertion of theside firing fiber into, during its use and its withdrawal from the sideentry port of the instrument channel, often referred to as the “workingchannel” of an endoscope; (q) an optimal outside diameter of the sidefiring device to enable it to be used through the working channel ofcommonly available endoscopes; and (r) an optimal adhesive material towithstand the elevated peak and average temperatures created at the endof the side firing device during use, and which does not significantlyabsorb the wavelength of laser energy being used, causing it to melt andallow the adhesively bonded components of the side firing device to movewith respect to each other or otherwise become degraded during use.

Common wisdom in the medical laser industry is that, to efficientlytransmit 80 or more watts of power from a Holmium or similar pulsedlaser or 80 or more watts of power from a diode or KTP laser, thehighest possible initial laser energy transmission efficiency should beemployed. Typically, this is done by beveling the distal end surface ofthe bared optical fiber and thermally fusing a distally closed-endedcapillary tube to the bared, beveled, distal end portion of the opticalfiber in the area of laser energy emission, by means known in the art.The reason for doing this is to eliminate the losses due to theglass-air-glass interface in the laser energy emission area caused bychanges in the index of refraction, an approximately 3.5% transmissionloss each time the index of refraction changes from glass to air toglass or an overall transmission loss of about 7%.

Closing the distal end of a capillary tube by thermal fusion typicallycauses stresses within the capillary tube to occur as it cools,weakening it, which can cause it to prematurely fail. Thermal fusion ofthe distal end portion of a capillary tube and fusion the capillary tubeto a bared optical fiber is typically done with a carbon dioxide or CO₂laser, an electric arc, a hydrogen flame or torch, or other means knownin the art.

Also, thermal fusing of a distally closed-ended capillary tube to thebared, distal end portion of an optical fiber has many disadvantages.First, the fused portion of the bared, distal end portion of the opticalfiber is mechanically fragile, which often requires a secondary means ofsecurement of the capillary tube to the optical fiber, such asadhesively bonding the proximal end portion of the capillary tube to theproximal end portion of the bared, optical fiber.

Second, due to the capillary tube being fixedly attached to the opticalfiber at more than one location, as the device rapidly vibrates duringuse (due to the equal and opposite mechanical forces from the formationand collapse of steam bubble during each laser pulse, as describedabove), the mechanically fragile optical fiber can fracture or becomedetached from the capillary tube, leading to additional losses andpremature device failure.

Third, thermal fusing of the capillary tube to the bared, distal endportion of the optical fiber in the area of laser energy emissiontypically entails some loss of flatness of the beveled, distal endsurface of the optical fiber due to its exposure to fusing temperaturesabove 1000° C. without exceeding the useful service temperature of thefiber's buffer (typically rated to between 200-400° C.) which in turncauses rapid cooling of the fused capillary tube and beveled distal endportion of the optical fiber. When these fused glass components rapidlycool, significant stresses are locked into the capillary tube and theoptical fiber, which may cause them to become more susceptible tofracture and failure during use.

Fourth, any air or other gas trapped between the optical fiber and thecapillary tube does not have the opportunity to escape when it becomesheated and expands during use, leading to pressure stresses beingexerted on the beveled distal end portion of the optical fiber and thecapillary tube, which can lead to their premature failure.

Although these fused devices can provide high in initial efficiency,some would fail after a few minutes of use at high laser power (forexample, at 100 watts of Holmium:YAG laser power).

Contrary to conventional wisdom, we made several attempts to develop aside firing device which did not utilize thermally fusing the capillarytube to the bared distal end portion of the optical fiber, in order toovercome the aforementioned disadvantages of conventional fusing. Weacted contrary to conventional wisdom in several respects denoted below.

First, we closed the distal end of the capillary tube by thermal fusionand annealed the capillary tube, allowing it to cool gradually atsuccessively lower temperatures in a series of time-controlled steps, toreduce any residual stresses in the closed-ended capillary tube prior toits being disposed over the beveled, distal end portion of the opticalfiber. Further, in some devices, we further tempered the outer surfaceof the capillary tube by rapid cooling, typically after the annealingcycle, to increase the strength in the outer surface of the closed-endedcapillary tube prior to its being disposed over the beveled, distal endportion of the optical fiber.

Second, rather than fusing the capillary tube to the bared, distal endportion of the optical fiber in the area of laser energy emission, weclose-fitted the capillary tube over the bared, distal end portion ofthe optical fiber, with a minimal gap between the optical fiber and thecapillary tube not exceeding 40 microns, preferably about 1 to 25microns, thus permitting the distal end portion to freely extend intothe cavity of the capillary tube without any constraint. The length ofdistal end portion extending into the cavity of the capillary tube is atleast two times the length of the bevel portion, which, of course,depends on the angle of the bevel. Stated in another way, the length ofthe distal end portion extending into the cavity is at least twice theratio the optical fiber outside diameter to the value of the bevel angletangent, i.e., 2×[optical fiber O.D./tan (bevel angle)].

Third, we close-fitted the capillary tube within the inner surface of aprotective metal sheath, with a gap between the capillary tube and theinner surface of the protective metal sheath that is filled withadhesive. The gap usually does not exceed 40 microns, and preferably isabout 1 to 20 microns.

The protective metal sheath disposed over the capillary tube, ispreferably composed of very pure gold, silver, copper, or aluminum,preferably 99.5% pure silver (compared to sterling silver, which is92.5% pure), which is highly reflective of the various wavelengths oflaser energy commonly used through side firing fibers, or a thin film orstrip of very pure gold, silver, copper, or aluminum is disposed overthe capillary tube, beneath the protective metal sheath opposite itslaser energy emitting area, which efficiently reflects aberrant laserbeams from the distal, beveled distal end surface of the optical fiberand the inner and outer surfaces of the capillary tube disposed over thetip of the optical fiber, out of the laser energy emission port. Forexample, 99.5% pure silver reflects about 97.9% of 532 fun KTP laseroutput, 98.8% of 980 nm diode laser output and 98.9% of 2100 nm Holmiumlaser energy.

We also found by thermal imaging that heat generated by aberrant,forwardly emitted laser light could overheat the distal end of theprotective metal sheath, causing damage to both the sheath and thecapillary tube. To minimize likelihood of such damage the distal end ofthe protective metal sheath is provided with an aperture aligned withthe optical axis of the optical fiber. If a Holmium laser is used, whoseenergy is highly absorbed by water, any laser energy escaping throughthe aperture in the sheath is harmlessly absorbed within a fewmillimeters (mm) of the irrigation fluid.

Fourth, to substantially reduce the rapid movement or vibration at thedistal end of the side firing device and to better enable it to be heldin position opposite the target tissue by the operator, we disposed arelatively rigid metal conduit or shaft over the optical fiber,including its buffer coating and any polymer cladding, from near theproximal end of the capillary tube to a point near the proximal end of ahandle or handpiece for ease of use by the operator, substantiallyreducing rapid movement or vibration at the distal end of the sidefiring device from the equal and opposite forces exerted against thedistal portion of the side firing device, as described above. The shaftor conduit can be metal or plastic, and preferably made of medical gradestainless steel. Preferably, the conduit has an ID of about 0.052″ andan O.D. of about 0.062″ for a wall thickness of about 0.005″ or about125 microns.

The handle provides better control over positioning of the side firingdevice opposite the target tissue by the operator and can contain avisible and/or tactile button on its exterior, preferably positioned180° opposite the direction of laser energy emission from the sidefiring fiber, as known in the art. When the operator's forefinger orthumb contacts the button, it points in the direction of laser energyemission. The handpiece or handle can be adhesively bonded to theexterior of the proximal end portion of the stainless steel shaft orsecured by other means known in the art.

Fifth, we fixedly attached the optical fiber to the interior of thestainless steel shaft near its proximal end, proximal to the area ofattachment of the handle or handpiece to the stainless steel shaft,enabling the bared, distal end portion of the optical fiber to moveslightly within the capillary tube during insertion into and withdrawalfrom the side entry port of the working channel of the endoscope andduring use. Securing the optical fiber to the stainless steel shaft, faraway from the capillary tube, rather than securing the optical fiber tothe capillary tube, leaving it free to move slightly when necessarywithin the capillary tube, prevented any localized stresses fromoccurring to the optical fiber both during transit through the sideentry port of endoscopes and during use, which in prior experimentscaused premature device failure during use.

Sixth, we created a channel or passageway within the stainless steelshaft to allow for expansion and contraction of air or other gassestrapped between the capillary tube and the distal end portion of theoptical fiber, which are heated during laser emissions. In the event thechannel within the shaft was not of adequate volume to equalize thepressure of such expanded air or other gasses, we provided a vent oropening in the stainless steel shaft near its proximal end, distal tothe point at which the optical fiber is fixedly attached to the shaft,to allow any excessive volume of such gasses to escape into theatmosphere, outside the patient and the endoscope. We took special carethat the fixed attachment method used to attach the optical fiber to theproximal end of the shaft terminated a sufficient distance proximallyfrom the vent in the shaft to not obstruct the vent.

High speed photography of the side firing device during use indicatedthat there were occasions where gasses were seen to escape and onoccasion contaminants were seen to burn up and escape from the spacebetween the capillary tube and the optical fiber and exit out of thevent in the stainless steel shaft.

Seventh, to avoid the stainless steel shaft's scraping against the metalinstrument channel of an endoscope, we encased the stainless steel shaftwithin a hollow, lubricious plastic sleeve, as described below, whichwas adhesively attached to the stainless steel shaft. We further crimpedthe proximal end of the reflective metal sheath over the distal end ofthe hollow, lubricious plastic sleeve, which was earlier disposed overthe stainless steel shaft encasing the optical fiber, making thetransition between the reflective metal sheath and the hollow,lubricious plastic sleeve as smooth as possible. If the transitionbetween the proximal end of the reflective metal sheath and the hollow,lubricious plastic sleeve is rough, it can cause the proximal end of thereflective metal sheath to catch on a portion of the metal instrumentchannel of an endoscope upon removal of the side firing fiber from theendoscope, potentially causing the reflective metal sheath to partiallyor completely become dislodged from the distal end of the side firingfiber, causing the side firing device to fail.

As mentioned above, during testing of side firing devices, we found thatentry and exit of the device from various commercially availableendoscopes was a challenge when the stainless steel shaft rubbed againstthe stainless steel, side entry port to the working channels of theseendoscopes, which ports may require the side firing device to passthrough a 10° or greater entry angle. Further, some of these endoscopeshad burrs where the side entry port joined the working channel, whichcaused devices without a smooth transition between the reflective metalsheath and hollow, lubricious plastic sleeve to have the reflectivemetal sheath become dislodged from the remainder of the device aftermultiple insertion/removal cycles.

To reduce the friction involved in these operations, a sleeve made of alubricious and durable plastic, such as polyether ether ketone (PEEK)(Invibio, Inc., West Conshohocken, Pa.), with a wall thickness of about125 microns can be provided to encase the stainless steel conduit orshaft. The side firing device can then be much more easily passedthrough and also resists scuffing when used in several commonlyavailable endoscopes with a working channel of 2.5 mm (7.5 French) orlarger, which allow sufficient space for infusing an irrigation liquid.Such endoscopes include those made by Karl Storz, Olympus, Richard Wolf,ACMI and others. The advantage of employing a thin tube of PEEK is itsrelatively low coefficient of friction and the ability to withstandscratching or scuffing when passing the side firing device into, movingit within during use and while removing it from the instrument channelof the endoscope a number of times.

When side firing devices were tested with an adhesive to (a) fixedlyattach the proximal end of the capillary tube to the distal end of thestainless steel shaft, (b) fixedly attach the distal end of thecapillary tube to the distal end of the reflective metal sheath, and (c)fixedly attach the proximal end of the reflective metal sheath to thedistal end of the stainless steel shaft and lubricious and durableplastic tubing, the device had significantly more functional longevitythan side firing devices tested with capillary tubes conventionallyfused to the bared, distal end portion of the optical fiber in the areaof laser energy emission, all other factors remaining constant.

When incorporating the above mentioned improvements, the adhesiveutilized must survive the high peak temperatures during lasing (150° to500° C. peak at the distal end of the side firing optical fiber device,determined by thermal imaging).

The adhesive must be able to resist such extremely high peaktemperatures, be substantially transmissive of the wavelengths of laserenergy used (e.g. from 300 nm to 2300 nm), and meet all sterilizationand biocompatibility requirements of a medical device. Suitableadhesives are the optically transparent U.S.P. Class VI epoxide epoxyresins that exhibit at least 85 percent transmission in the range ofabout 400 to about 2500 nanometers and has a service temperature in airof at least about 100° C., preferably at least 120° C., more preferablyabout 135° C. Preferably, the adhesive has an average air servicetemperature of about 135° C., is substantially transparent to laserenergy at 300 to 2500 nm and has a pull strength, after curing, of above20 lb-f. with a 125 micron bond gap. A particularly preferred adhesiveabsorbs only about 6% of KTP laser energy, 6% of diode laser energy at980 nm and 6% of CTH:YAG or Holmium laser energy.

When tested in a water bath with the distal end of a 550 micron corefiber placed in contact with the side wall of a capillary tube with bothends sealed with a strip of very pure silver with a wall thickness of250 microns coated with this adhesive adhered to the back side of thecapillary tube, when 10 Watts of Holmium Laser power was emitted at 1joule per pulse at 10 pulses per second for 10 minutes, there was novisible degradation of the adhesive or the underlying silver strip.

When side firing devices employing the aforementioned improvements weretested, their transmission efficiency and tissue vaporization rate wereconsistently higher and their functional longevity was significantlylonger lasting, compared to current commercially available side firingdevices.

Sixty side firing devices embodying the present invention were tested,and they were able to consistently achieve without failure at least 90minutes of continuous laser emission at 80 to 135 watts of Holmium:YAGlaser input power.

Further, and as significant, these side firing devices did notsignificantly decline in laser transmission efficiency and tissuevaporization rate, compared to commercially available side firingdevices.

We conducted a series of experiments with various optical fibers tominimize losses. We discovered that a Low-OH optical fiber with a corediameter of about 450 microns could accept and transmit up to 150 wattsof Holmium laser power. Optical fibers with larger core-to-clad ratioswere found to have less overall losses than those with smaller core toclad ratios (e.g. 1:1.2 vs. 1:1.1).

Increasing the fiber core to cladding ratio is relatively expensive, asfiber cladding in glass fibers is typically made by fluorinating thefused silica of the cladding to create a lower index of refraction thanthat of the core of the optical fiber. However, substantially the samedifference in the index of refraction between the outer glass layer ofthe fiber and the environment outside the optical fiber can be achievedby other means. We experimented with optical fibers with a very smallcore to clad ratio (e.g. 1:1.05) with an undoped thicker outer layer or“overjacket” of fused silica over the thinner, fluorinated, fused silicacladding, made as part of the overall optical fiber drawing process.This unique optical fiber construction is less expensive thanconventional optical fibers used in medical applications, due to thethinner layer of fluorinated glass cladding, and provides the addedbenefit of a slightly larger index of refraction difference between theouter, undoped, fused silica overjacket of the optical fiber and theenvironment, which, allows a slightly higher angle of reflection fromthe beveled, distal end surface of the optical fiber. When testing sidefiring fibers of this construction, we found that the lateral orside-firing initial transmission efficiency was slightly better thanconventional optical fibers with full thickness fluorinated cladding, ata fraction of the cost.

During our experiments, we found that there was an optimal core tooverall combined fluorinated cladding and undoped, fused silicaoverjacket ratio to obtain the advantages of this approach, withoutsacrificing either the amount of space remaining available for a greaterwall thickness of the capillary tube, or the space available for aprotective, metal sheath over the capillary tube, to avoid the outsidediameter of the side firing device exceeding 2.3 mm and not fittingwithin the 2.5 mm or larger instrument channel of many, commonlyavailable endoscopes, leaving a sufficient space for infusing anirrigation fluid.

To achieve optimal laser energy transmission efficiency, we discoveredthat the optimal core to overall combined fluorinated fused silicacladding and undoped fused silica overjacket ratio was about 1:1.25 to1:1.39, preferably about 1:1.34. Further, we found that if the core toouter glass size ratio is greater than about 1:1.4 with a fiber coresize large enough to transmit up to 150 watts of Holmium:YAG laserpower, the capillary tube cannot have a sufficiently large wallthickness to endure the above described hydrothermal erosion for asufficient period of time (e.g. 60 minutes or longer), withoutincreasing the O.D. of the device beyond about 2.17 mm.

According to prior art, for efficient transmission of laser energy, thecore to cladding ratio (not core to overall glass size) of the opticalfiber should be 1:1.4 or higher. However, due to the relative mechanicalweakness of the fluorinated glass cladding, as compared to undopedsynthetic fused silica, a side firing angle at or below that which wouldnormally be needed for total internal reflection so that greater thanabout 90% of electromagnetic radiation reflected by the reflectingsurface is incident on the particular area at below a critical angle fortransmission through the transmitting surface in the lateral direction,inadequate wall thickness of the capillary tube disposed over thebeveled, distal end portion of the optical fiber, and its reducedresistance to back reflected laser energy, back splatter degradation andhydrothermal erosion, the commercially available side firing devicesachieve an overall laser energy transmission efficiency of only about90% and sometimes fail before vaporizing 30 to 80 grams of soft tissue,such as that of the male prostate.

We discovered that the thin fluorinated fused silica cladding,surrounded by an undoped fused silica overjacket, as described above,enabled the optical fiber to be beveled at an angle greater than thecritical angle for total internal reflection from standard equationsknown in the art, so that over 90% of the laser energy is reflected bythe beveled, distal end surface of the optical fiber.

When testing different angles of distally beveled optical fibersurfaces, we found that optical fibers of different construction haddifferent efficiency curves. While some fibers with smaller core to cladratios performed very close to the theoretical maximum angle for TIR(for the 2.1 μm wavelength with 0.22 NA Low-OH fibers, the maximumtheoretical angle for TIR is 37°), optical fibers with larger core toclad ratios, using the previously described thin, fluorinated, fusedsilica cladding surrounded by a thicker, undoped, fused silicaoverjacket, performed differently from theory. For these types of sidefiring fibers, the maximum theoretical angle for TIR could be exceededwith an increase in overall laser energy transmission efficiency, due totheir outer layer or overjacket of undoped fused silica having aslightly higher index of refraction than a typical optical fiber with acustomarily thick and more expensive fluorinated glass cladding.

Using such undoped fused silica overjacketed optical fibers on top of athin cladding of fluorinated fused silica, we tested side firing fiberswhose distal ends were beveled and mechanically polished at an angle ofbetween 35° and 42° relative to the optical axis of the optical fiber in1° increments with a Holmium laser. We found that their laser energytransmission efficiency improved from about 84% at 35° and increasedeach degree up to about 95% at 41°, but rapidly decreased in efficiencyto below about 84% at an angle of 42° or greater.

To maximize laser energy transmission efficiency, the beveled, distalend surface angle is optimized for a combination of a given laser'swavelength, numerical aperture, cladding, and other optical fiberconstructional details, and is closely controlled. Thus, for thefollowing experiments with the same Holmium laser and side firing fiberconstruction, we maintained the beveled, distal end surface of theoptical fiber at an angle of between 40° and 41°, resulting in theemission of laser energy, according to Snell's Law, at an angle of about80° to 82° from the axis of the optical fiber.

We then experimented with determining the magnitude of the differentlosses at different spacial orientations from the distal end of deviceswith the aforementioned 40° to 41° beveled, distal end fiber surface andour previously described combined cladding and overjacket construction.We found that while the majority of losses were directed opposite theprimary, side firing emission direction, there were additional smallerlosses directed to the left and right sides of the primary, side firingemission direction, as well as smaller losses directed both forward andbackward along the longitudinal axis of the optical fiber. Ininvestigating these losses, we found that the flatness of the beveled,polished, distal end surface of the optical fiber can have a significantimpact on the magnitude of these losses.

When testing the flatness of the beveled, distal end surfaces of opticalfibers with a Michelson interferometer, utilizing a 635 nm diode laser,we discovered that the aberrant reflections or losses, althoughrelatively small, could be reduced by over 60% by decreasing themeasured curvature of the beveled, distal end surface of the opticalfiber from 5.3 microns to 1.3 microns. This increased flatness allowsmore consistency in laser transmission efficiency among all devices ofthe same configuration, and is easily determined by measuring surfaceflatness directly or by measuring the losses from the sides of the fiberand ensuring that they were below a certain percentage, which can beequated to a specific surface flatness.

During the construction of various side firing devices, we noticed thatthe distal, leading edge of the optical fiber's beveled surface wasfragile and susceptible to damage during assembly, subsequent handlingand use. We call the thin leading edge of the beveled, distal endsurface of the optical fiber the “tip”, and we call the thickest portionof the beveled, distal end surface of the optical fiber the “root”. Wealso discovered that, as optical fibers in the drawing process aretraditionally wound and stored on a roll or spool, when the opticalfiber is un-spooled, it has taken a slight set, so it is not quitestraight when laid naturally on a flat surface. We were able to takeadvantage of this fiber set to reduce the susceptibility of the tip todamage by orienting the fiber during polishing and assembly, so that thetip is aligned with the section of the fiber furthest away from thecenter of the bend radius (e.g. the very outside portion of the fiberset) and the root is aligned with the section of the fiber closest tothe center of the bend radius (e.g. the very inside portion of the fiberset).

By using this technique, we discovered that, when the tip is insertedinto the capillary tube, the root tends to rest against the innersurface of the capillary tube opposite the area of laser transmission,with a small gap between the tip and the inner surface of the capillarytube through which light is transmitted. This prevents significantstresses on the tip that are present and detectable with either amicroscope or a polarimeter, compared to when the opposite of the abovepositioning technique is used. This has also substantially reduced theoccurrence of chips at the tip of the fiber during manufacture,handling, and use.

As one of the objectives of this invention is a highly durable sidefiring device, with the longest possible functional longevity, thematerial and dimensions of the capillary tube are significant. Duringour testing, we found that natural fused silica capillary tubes did notwork as well, and their consistency and durability was not as desirable,as natural fused silica has a certain level of natural defects. If thosedefects are present in the portion of the capillary tube through whichlaser energy is transmitted, the device had shorter functional longevityand lower reliability.

We found that the use of synthetic fused silica capillary tubes, formedby inside or outside vapor deposition, enabled the side firing device toachieve enhanced longevity. Further, we discovered that fluorinated,synthetic fused silica capillary tubes, instead of fluorinated naturalfused silica, can be used to further increase the longevity of the sidefiring device, as fluorinated, synthetic fused silica reduces the rateat which hydrothermal erosion occurs in the capillary tube during use,with little increase in device cost, due to their short length.

From a dimensional standpoint, we found as the wall thickness of thecapillary tube in the area through which laser energy is transmitted wasincreased, the functional longevity of the capillary tube and the sidefiring device was increased. Upon testing capillary tubes of bothfluorinated and unfluorinated synthetic fused silica with various wallthickness, we also discovered that, to enable the capillary tubeencasing the beveled, distal end portion of the optical fiber to bestendure hydrothermal erosion, back splatter degradation and backreflection of laser energy, the capillary tube should have a wallthickness of at least about 500 microns in the area through which laserenergy is transmitted.

Thus, within the overall size constraints of the device, minimizing theID of the capillary tube (e.g. 650 microns, including the approximately25 micron gap described above) and maximizing its OD (e.g. 1650 nm or1.65 mm), enabled us to utilize a capillary tube with a 510 micron wallthickness to resist the above-described damage, after encasing thecapillary tube with an optional, hollow, open-ended metal sheath with awall thickness of 300 microns with a port for emission of the laserenergy, as described above, for an overall device OD of 2.3 mm, for adevice with a high functional longevity and high reliability, all otherfactors remaining constant.

Capillary tubes can be formed with an eccentric inner hollow bore orchannel, without changing their outer, circular diameter. Thesecapillary tubes allow the wall thickness in the portion through whichlaser energy is transmitted to be significantly larger (e.g. up to about750 microns) than the wall thickness in the portion opposite laseremission (e.g. as little as about 270 microns), which allows increasedfunctional longevity of the side firing device, due to the thicker wallof the capillary tube in the path of laser energy emission being moreresistant to hydrothermal erosion, back splatter degradation and backreflection of laser energy, where all other factors remain constant.

In laboratory bench testing, thirty (30) side firing devices wereconstructed in accordance with the present invention, as describedherein with the optical fiber having a core diameter of about 450microns, encased by a thin, fluorinated, fused silica cladding and anundoped, synthetic fused silica overjacket, with a combined cladding andover-jacket wall thickness of about 75 microns, for a core to overallglass size of about 1:1.34, disposed within a distally closed-endedcapillary tube of synthetic fused silica, with a wall thickness of 510microns, with a gap of about 28 microns between the exterior of theoptical fiber and the interior of the capillary tube, covered by ahighly pure silver, hollow, open-ended metal conduit or sheath with awall thickness of 300 microns, with a gap of about 20 microns betweenthe exterior of the capillary tube and the interior of the silversheath, for an overall O.D. of the side firing optical fiber device ofabout 2.3 mm.

When 100 or more watts of Holmium:YAG laser power was transmittedthrough the above described devices, using a automated robotic arm tomove the side firing device at a uniform speed at a uniform positionabove soft animal (porcine) tissue in a water bath, their initialtransmission efficiency averaged 91%, they were able to vaporize anaverage of 3.19 grams of soft animal tissue per minute over a period of90 minutes, and they were all functioning satisfactorily after 90minutes of lasing, with little reduction in tissue removal rate, nocracking or failure of the capillary tubing, no tip dislodgement, orother malfunctions, and with only normal expected device degradation.

Thirty (30) devices of the same construction were tested on the sameHolmium laser under the same conditions by an independent testinglaboratory, whose testing confirmed the above-described results.

In actual use by a surgeon manually in the prostate of a patient, thetissue vaporization rate is expected to be substantially lower, about1.5 grams per minute, over a period of about 90 minutes, as Holmiumlaser power is lost vaporizing irrigation liquid if the side firingdevice is held too far away from the target tissue and, if the sidefiring device is held so that it touches the target tissue, thecapillary tube can be contaminated and degraded.

Further, these features enable a side firing device constructed asdescribed above to be cleaned after use, steam sterilized and reused,perhaps several times, significantly reducing its cost to hospitals,surgery centers and others.

As shown in FIG. 1, side firing device 10, constructed in accordancewith the present invention, utilizes a source of laser energy 11, whichtransmits its laser energy into optical coupler 12, which focuses anddelivers the laser energy into the proximal end of fused silica core 13(shown in FIG. 2) of optical fiber 14, which extends to near the distalend of side firing device 10. Laser energy source 11 generates whateverwavelength of laser energy is desired, including without limitation anexcimer, KTP, diode, Nd:YAG, Thulium:YAG, or Holmium:YAG laser,preferably a Holmium:YAG laser at a wavelength of about 2100 nm.

As shown in FIG. 2, optical fiber 14 of side firing device 10 of thepresent invention has a fused silica core 13 with a diameter of about450 microns and a refractive index of about 1.461 at 532 nm, 1.451 at980 nm, about 1.450 at 1064 nm, about 1.439 at 1900 nm and, preferably,about 1.437 at about 2100 nm. Core 13 is surrounded by a thin,fluorinated, fused silica cladding 15 with a thickness of about 11microns with a sufficiently lower refractive index to cause totalinternal reflection of light, with a core 13 to cladding 15 ratio ofabout 1:1.05.

Fluorinated, synthetic fused silica cladding 15 is encapsulated by anouter overjacket 15 a of undoped, synthetic fused silica, with a wallthickness of about 65 microns, which brings the actual glass outerdiameter (O.D.) of optical fiber 14 to about 600 microns, and thecombined cladding 15 and overjacket 15 a bring the core 13 to overallcombined fluorinated fused silica cladding 15 and undoped fused silicaoverjacket 15 a ratio to about 1:1.34. The distal end portion of outeroverjacket 15 a of optical fiber 14 was earlier stripped of any polymercladding and protective buffer coating 31.

The distal end of optical fiber 14 has distal end surface 16 with abevel angle of 40° to 41° relative to the optical axis of the fiber. Thebeveled, distal end portion of optical fiber 14 is disposed within acavity of distally closed-ended capillary tube 17, which has a wallthickness of 100 to 1000 microns, preferably about 510 microns.Capillary tube 17 can be made of natural fused silica, but is preferablymade of synthetic fused silica to reduce imperfections and increaselaser efficiency and durability, and is most preferably made offluorinated, synthetic fused silica to increase its resistance to backsplatter degradation and hydrothermal erosion when used in a liquidenvironment. Undoped fused silica overjacket 15 a and capillary tube 17each have wall thicknesses sufficient to endure a significant amount ofuse, prevent chipping of undoped fused silica overjacket 15 a,mechanical damage, laser energy reflected back from the target tissue,back splatter degradation and hydrothermal erosion. Capillary tube 17 isnot attached to, i.e., is spaced from, undoped, synthetic fused silicaoverjacket 15 a of optical fiber 14.

Capillary tube 17 has a closed distal end 18. This is accomplished bythermally fusing the distal end of capillary tube 17 to close its distalend 18, using CO₂ laser energy, an electric arc, a hydrogen flame orother means known in the art that ensure no contaminants are introducedinto the capillary tube 17 during this process. After closing the distalend 18 of capillary tube 17, capillary tube 17 is further processed byannealing using a series of small, timed reductions in temperature fromits maximum dwell temperature of about 1200° C. by about 50° C. eachover a period of about 20 minutes each, to avoid the formation ofresidual stresses in capillary tube 17.

Capillary tube 17 is close-fitted over the beveled, distal end portionof bared optical fiber 14 with a gap between the fiber and sidewall ofcapillary tube 21 not exceeding 40 microns, preferably about 1 to 25microns. Gap between fiber and capillary tube 21 is not filled with anadhesive or other material, but is left open. Gap between fiber andcapillary tube 21 allows air, other gasses or materials trapped betweenclosed distal end 18 of capillary tube 17 and beveled, distal endsurface 16 of optical fiber 14, which are heated during the emission oflaser energy, to expand and not over-pressurize and damage capillarytube 17 or optical fiber 14.

Laser energy is laterally emitted from beveled, distal end surface 16 ofoptical fiber 14 by total internal reflection, due to capillary tube 17providing an air interface with a lower index of refraction than that ofcore 13 of optical fiber 14 opposite beveled distal end surface 16 ofoptical fiber 14. The laser energy passes through laser energy emissionarea 19 of capillary tube 17, and exits as shown by arrows 20 at anangle of about 80° to 82°.

Capillary tube 17 is close-fitted within internally reflective metalsheath 23, which is preferably made of very pure gold, silver, oranother reflective metal, most preferably 99.5% pure silver (forcomparison, sterling silver is 92.5% pure). Metal sheath 23 is highlyreflective of the wavelength of laser energy typically used through sidefiring device 10. For example, 99.5% pure silver reflects about 98.9% ofHolmium laser energy at 2100 nm, about 97.9% of KTP laser energy at 532nm and about 98.8% of diode laser energy at 980 nm. Optionally,reflective metal sheath 23 may be made of a metal coated with adielectric or other coating known in the art which is highly reflectiveto the wavelength of light being transmitted.

Reflective metal sheath 23 has a wall thickness of 10 to 1000 microns,preferably about 300 microns and is close-fitted over capillary tube 17.Gap between capillary tube and reflective metal sheath 26 is no morethat 40 microns, preferably about 10 to 20 microns, and is filled withan adhesive 22. Protective metal sheath 23 protects capillary tube 17from mechanical damage, laser energy reflected back from the targettissue, back splatter degradation and hydrothermal erosion, whichresults in an overall O.D. of side firing device 10 of about 2.3 mm, andenables it to pass in and out of 2.5 mm (7.5 French) or larger diameterinstrument channels of commonly available endoscopes. The inner surfaceof reflective metal sheath 23 also reflects aberrant beams of laserenergy from imperfections in beveled surface 16 of optical fiber 14 andcapillary tube 17 back through optical fiber 14, most of which pass outof laser energy emission port 24 in protective metal sheath 23.

Capillary tube 17 is not fused or otherwise fixedly attached to fusedsilica overjacket 15 a of optical fiber 14 at area 19 or at any otherlocation. No adhesive 22 is used to attach capillary tube 17 to fusedsilica overjacket 15 a of optical fiber 14 at gap 21 or any other place.Instead, capillary tube 17 is positioned during assembly andclose-fitted within hollow conduit 30 and reflective metal sheath 23,and is fixedly attached to conduit 30 and sheath 23 by adhesive 22.

Laser energy emission port 24 in reflective metal sheath 23 is disposedover the region of laser energy emission 19 of capillary tube 17, whichis disposed 180° opposite the distal, beveled end surface 16 of opticalfiber 14. The distal end of reflective metal sheath 23 is provided withan aperture 25 to permit any forwardly emitted laser energy to exitwithout overheating metal sheath 23 or capillary tube 17. Aperture 25can also serve as a detection system of capillary tube failure by theuser if the forwardly emitted laser energy substantially and quicklyincreases during use. As shown, the distal end of metal sheath 23preferably is bulbous or rounded, but it can be blunt, conical, sharp,syringe-needle shaped, trocar shaped or of any other desired shape.

To prevent mechanical damage to optical fiber 14 proximal to theproximal end of capillary tube 17, hollow conduit 30 is disposed overoptical fiber 14 to resist the equal and opposite forces exerted uponthe distal end portion of side firing device 10 by the emission of laserenergy, preferably by forces exerted by steam bubbles formed by theemission of Holmium laser energy at a wavelength of 2100 nm in anaqueous liquid field and the resulting acoustic shock from the collapseof said steam bubbles as described earlier, enabling the operator tobetter maintain the side firing device in position opposite the targettissue during use.

As shown in FIG. 3, hollow plastic or metal shaft 30 is fixedly attachedby adhesive 22 to the interior of handle 32 near its proximal end. Shaft30 is also fixedly attached to optical fiber 14 near its proximal end byone or more crimps 39, by both adhesive 22 and one or more crimps 39, orby other means known in the art.

To improve the ease of passing side firing device 10 through theinstrument channel of commonly available endoscopes (not shown), some ofwhich may have a side-entry port (not separately shown), which mayintersect with the instrument channel of the endoscope at an angle ofabout 10° or more, and may have burrs or other imperfections where theside-entry port intersects with the instrument channel, hollow plasticor metal shaft 30 can be coated with a thin film or covered by a hollow,plastic outer sleeve 29, which may be made of a lubricious material,such as Fluorinated Ethylene Propylene (Teflon® FEP) or EthyleneTetrafluoroethylene (Tefzel® ETFE), made by the DuPont Co. ofWilmington, Del., or, preferably, to resist scuffing, lubricious plasticsleeve 29 is preferably made of a durable and lubricious plastic, suchas PEEK (Invibio, Inc., West Conshohocken, Pa.). Plastic lubricioussleeve 29 is fixedly attached to hollow plastic or metal shaft 30 byadhesive 22 or other means known in the art.

About half of the proximal end of capillary tube 17 is fixedly attachedto the distal end of shaft 30 by adhesive 22. To maintain the integrityof and prevent the unwanted dislodgement of reflective metal sheath 23during removal from endoscopes, the proximal end of reflective metalsheath 23 is swaged or otherwise collapsed over the distal end oflubricious plastic sleeve 29, to allow for a smooth mechanicaltransition between lubricious plastic sleeve 29 and reflective metalsheath 23.

To resist the equal and opposite forces on the distal end portion ofside firing device 10 from steam bubble explosions and photo acousticshock waves, as described earlier, hollow metal or plastic shaft 30extends over optical fiber 14, from near the middle of capillary tube 17(as shown in FIG. 2) to near the proximal end of handle 32.

Handle 32 may be fixedly attached to the exterior of hollow plastic ormetal shaft 30 by adhesive 22. Handle 32 may optionally be attached tothe exterior of metal shaft 30 and moveable (not separately shown) withrespect to the portion of optical fiber 14 extending from the proximalend of protective metal sheath 23 to the source of laser energy 11, bymeans known in the art. Handle 32 optionally has a fixed orientationknob 34 positioned on handle 32, preferably positioned 180° opposite thebeveled, distal end surface 16, and opposite the area of laser emission27, to allow the user's finger or thumb, when placed on the orientationknob 34, to point in the direction of laser emission.

Hollow metal shaft 30 is fixedly attached to buffer coating 31 ofoptical fiber 14, proximal to vent opening 33 in shaft 30, by one ormore crimps 39 in shaft 30 to buffer coating 31 of optical fiber 14, byadhesive 22, or by other means known in the art. To allow any air orgasses trapped between beveled, distal end surface 16 of optical fiber14 and capillary tube 17, which are heated and expanded during thetransmission of light, to escape into the atmosphere and avoid abuild-up of pressure between these components, hollow metal or plasticshaft 30 has channel 38 extending proximally from the proximal end ofcapillary tube 17 to opening or vent 33, distal to the attachment ofoptical fiber 14 to the interior of metal or plastic shaft 30 by one ormore crimps 39, adhesive 22, and the like.

In addition to shaft 30 resisting rapid movement or vibration of sidefiring device 10, the presence of hollow shaft 30 also makes it easierfor the operator to maintain the distal end of side firing device 10 ata desired position opposite the target tissue during use.

To protect optical fiber 14 as it exits the proximal end of handle 32from excessive bending or breakage, and to allow ease of rotation ofarea of laser energy emission 27 within port 24 in protective metalsheath 23, snap collar 35 is inserted into the proximal end of handle 32during assembly. Prior to insertion of snap collar 35 into the proximalend of handle 32, snap collar 35 is attached to the distal end ofprotective jacket 36 and strain relief 37 by adhesive 22, or the like.

Protective jacket 36 has a wall thickness of about 700 microns andextends about 100 microns from within the proximal end of handle 32 overstrain relief 37. Strain relief 37 has a wall thickness of about 400microns and extends from within the proximal end of handle 32 and isabout 10 cm in length. Protective jacket 36 and strain relief 37 protectoptical fiber 14 from being bent excessively as it enters handle 32 andhollow shaft 30, as known in the art. Protective jacket 36 also protectsoptical fiber 14, including buffer coating 31 on optical fiber 14,during use by preventing clamping of optical fiber 14 to surgicaldrapes, gowns, and the like, and prevents damage to optical fiber 14during handling before or after use of side firing device 10.

Reducing the diameter of core 13 of optical fiber 14 to 450 microns,from the customary 550 to 600 micron core diameter of optical fiberscommonly used in side firing devices made by others, results in anincrease in the energy density or fluence of the emitted laser energybeam, as shown by arrows 20. For example, at 2 joules per pulse at 50 Hz(100 watts) of Holmium laser energy, the fluence from the area of laseremission 27 of optical fiber 14 is 23.6 kW/cm², compared to 18.0 kW/cm²if the diameter of core 13 of optical fiber 14 was 550 microns and thesame 100 watts of Holmium:YAG laser energy was transmitted throughoptical fiber 14.

Similarly, if 180 watts of KTP (532 nm) laser power is used, the powerdensity of the emitted laser beam with a core 13 of optical fiber 14having a diameter of 450 microns from the area of laser emission 27 is42.5 kW/cm², compared to 32.4 kW/cm² if the diameter of core 13 ofoptical fiber 14 was 550 microns and the same 180 watts of KTP (532 nm)laser power was transmitted through optical fiber 14. Furthermore, if300 watts of diode (980 nm) laser power is used, the power density ofthe emitted laser beam with a core 13 of optical fiber 14 having adiameter of 450 microns is 70.8 kW/cm², compared to 54.0 kW/cm² if thediameter of core 13 of optical fiber 14 was 550 microns and the same 300watts of diode (980 nm) laser power was transmitted through opticalfiber 14.

The laser light transmission efficiency of side firing device 10,constructed in accordance with the preferred embodiment of the presentinvention, is at least about 91% when used with Holmium laser energy,about 90% when used with KTP (532 nm) lasers and about 91% when usedwith diode (980 nm) lasers.

As can be seen in FIG. 4, optical fiber 14 is comprised of core 13,which is preferably made of fused silica with an O.D. of about 450microns, surrounded by a preferably fluorine-doped fused silica cladding15, more preferably synthetic fused silica, which has fewerimperfections and impurities than natural fused silica. Cladding 15 hasa wall thickness of about 11 microns and an O.D. of about 472 microns,and outer overjacket 15 a, of preferably undoped fused silica, mostpreferably undoped, synthetic fused silica, has a wall thickness ofabout 65 microns and an O.D. of about 600 microns.

Capillary tube 17, which is made of undoped fused silica, preferablyundoped, synthetic fused silica and most preferably of fluorine-doped,synthetic fused silica, as synthetic fused silica has fewerimperfections and impurities than natural fused silica. Furthermore,fluorinated, synthetic fused silica has higher resistance to backreflected laser energy, back splatter degradation and hydrothermalerosion. Capillary tube 17 is close-fitted over the bared, distal endportion of optical fiber 14 (after any optional polymer cladding andbuffer coating is earlier removed), with gap 21 between capillary tube17 and optical fiber 14 not exceeding about 40 microns, preferably about1 to 25 microns.

Capillary tube 17 has a wall thickness of about 510 microns and an O.D.of about 1650 microns. Capillary tube 17 is also close-fitted within theinner surface of hollow, reflective metal sheath 23, which has a wallthickness of about 300 microns, with gap 26 between capillary tube 17and metal sheath 23 not exceeding about 40 microns, preferably about 10to 20 microns. Gap 21 is not filled with an adhesive, while gap 26 isfilled with adhesive 22.

As shown in FIG. 5, capillary tube 17 has the same O.D. as capillarytube 17 shown in FIG. 4. In this more preferred embodiment of device 10of the present invention, capillary tube 17 has eccentric channel 40,which is oriented to provide the greatest wall thickness 41 of capillarytube 17 at the area of laser energy transmission 19 from capillary tube17, to provide added protection to capillary tube 17 from backreflection of laser energy, back splatter degradation and hydrothermalerosion, as described earlier. The relatively thinner wall thickness 42of capillary tube 17 can be seen at the bottom of reflective metalsheath 23.

As seen in FIG. 6, the distal end of side firing device 10 showsreflective metal sheath 23, port 24 in sheath 23, capillary tube 17,optical fiber 14, and beveled distal end surface 16 of optical fiber 14.This image was taken prior to any use of laser energy through device 10on tissue.

As seen in FIG. 7, in an image taken after transmission of 107 watts ofHolmium laser power for ninety (90) minutes through side firing device10 of the present invention on tissue, reflective metal sheath 23 showssome pitting distal to port 24, due to damage from laser energyreflected back from the target tissue and back splatter degradationduring use.

This demonstrates that sheath 23 assists in protecting capillary tube 17during use, as the back reflected laser energy, back splatterdegradation and hydrothermal erosion, in the absence of reflective metalsheath 23, would have been incident on the distal end of capillary tube17. Also, capillary tube 17 has been somewhat eroded due to hydrothermalerosion at area of laser energy emission 27, but has not beensignificantly damaged by laser energy reflected from laser energyreflected back from the target tissue and back splatter degradationduring use. Also, the laser energy transmission efficiency of device 10of the present invention has not been impaired to the point ofunusability, it is not close to failure and laser energy can continue tobe emitted from device 10.

A side firing device constructed in accordance with the preferredembodiments of the present invention described above can be used, forexample, without limitation, for at least one of the following medicalpurposes:

(a) to vaporize excess, benign prostate tissue to relieve itsobstructing urine flow (BPH);(b) to vaporize excess nucleus pulposa tissue of a herniated spinal discto relieve the pressure of the disc on nerves in the spine (laser discdecompression);(c) to vaporize cartilaginous tissue of the facet and, if necessary, asmall amount of non-load bearing bone of the facet, to enable anendoscope and the side firing device to gain entry to the foraminalspace in the spine and vaporize nucleus pulposa tissue extruded from aruptured spinal disc to relieve its pressure on nerves in the spine(endoscopic laser foraminoplasty);(d) to coagulate/vaporize a uterine fibroid tumor, which bleedsprofusely if cut, the side firing device is inserted and the tumor iscoagulated/vaporized from the inside, by rotating the laser beam fromthe side firing device like the beacon of a lighthouse; and(e) to coagulate/vaporize a solid tumor, the side firing device isinserted into the tumor, and the tumor is coagulated/vaporized from theinside, by rotating the laser energy beam from the side firing devicelike the beacon of a lighthouse.

While this invention is susceptible of embodiment in many differentforms, there are shown in the drawings and will be described in detailherein specific embodiments thereof, with the understanding that thepresent disclosure is to be considered as an exemplification of theprinciples of the invention and is not to be limited to the specificembodiment illustrated.

Numerous variations and modifications of the embodiments described abovecan be effected without departing from the spirit and scope of the novelfeatures of the invention. It is to be understood that no limitationwith respect to the specific apparatus illustrated herein is intended orshould be inferred. It is, of course, intended to cover by the appendedclaims, all such modifications as fall within the scope of the claims.

We claim:
 1. A side firing laser device comprising a conduit having anopen distal end; a closed end, transparent capillary tube defining acavity and mounted to a distal end portion of the conduit so that thecavity is in communication with the conduit; an optical fiber in theconduit, adapted for coupling to a laser energy source, including aproximal end portion for coupling to the laser energy source and abeveled distal end portion extending into said cavity; a bulbous,internally reflective metal sheath about the capillary tube and mountedto the conduit; the distal end portion of the optical fiber extendingfreely into said cavity; and the metal sheath defining a side portproviding an outwardly path for laser radiation emitted from the distalend of the optical fiber and an aperture aligned with optical axis ofthe optical fiber.
 2. The side firing laser device in accordance withclaim 1 wherein end surface of the beveled distal end portion defines anangle in the range of about 40 degrees to about 41 degrees with theoptical axis of the optical fiber.
 3. The side firing laser device inaccordance with claim 1 wherein clearance between cavity sidewall andthe beveled distal end portion is not more than 40 microns.
 4. The sidefiring laser device in accordance with claim 1 wherein clearance betweencavity sidewall and the beveled distal end portion is in the range ofabout 1 to 25 microns.
 5. The side firing laser device in accordancewith claim 1 wherein the beveled distal end portion terminates in a flatsurface having a surface curvature of no more than about 5 microns. 6.The side firing laser device in accordance with claim 1 wherein thebeveled distal end portion terminates in a flat surface having a surfacecurvature of no more than about 1.3 microns.
 7. The side firing laserdevice in accordance with claim 1 wherein the optical fiber has a corediameter of about 450 microns and a core-to-cladding ratio of about1:1.05.
 8. The side firing laser device in accordance with claim 1wherein the capillary tube has a wall thickness in the range of about100 to about 1000 microns.
 9. A side firing optical fiber device,comprised of a source of laser energy, an optical fiber opticallycoupled to the source of laser energy, the optical fiber having a coreof fused silica and an exterior cladding of fused silica doped with amaterial that reduces its refractive index, the distal end of theoptical fiber being beveled, and the beveled, distal end of the opticalfiber being encased by a distally closed-ended, fused silica capillarytube, providing an air interface opposite the beveled, distal endsurface of the optical fiber necessary for total internal reflection oflaser energy, which includes at least one of the following: (a) anoptical fiber having an optimal core diameter of about 450 microns, ableto efficiently transmit the high levels of laser energy with wavelengthscommonly used through side firing devices; (b) an optical fiberoptimally having a cladding of fluorinated fused silica, preferablyfluorinated synthetic fused silica, with a wall thickness of about 11microns, for a core to cladding ratio of about 1:1.05, providing thenecessary lower refractive index required for efficient transmission oflaser energy through the optical fiber at substantially lower cost thanthe greater 1:1.1 to 1:1.2 core to cladding ratios commonly used in highpower optical fibers; (c) an optical fiber optimally having an outeroverjacket of undoped fused silica, preferably undoped synthetic fusedsilica, with a wall thickness of about 65 microns, with a combined coreto cladding and overjacket ratio of about 1:1.34, providing optimalprotection to the thin, leading edge of the beveled, distal end surfaceof the optical fiber; (d) an optical fiber having an optimal OD of about600 microns, which is sufficiently small to enable as large as possiblewall thickness of a distally closed-ended capillary tube to be used toencase the beveled, distal end portion of the bared optical fiber; (e)an optical fiber having its distal end beveled at an angle of 35° to45°, optimally at an angle of about 40° to 41° providing total internalreflection of laser energy at an angle of 80° to 82° laterally from theaxis of the optical fiber; (f) a beveled, distal end surface of theoptical fiber having an optimal flatness, with a curvature across thesurface of not more than about 5 microns, most optimally not more than1.3 microns to minimize laser energy transmission losses; (g) an opticalfiber having taken a set while stored on a spool and, when unwound fromthe spool for further manufacture, using this set to optimally positionthe thin leading edge of the beveled, distal end surface of the opticalfiber away from contact with the inner surface of the distallyclosed-ended capillary tube close-fitted over the beveled distal endportion of the optical fiber; (h) a capillary tube having a wallthickness of about 100 to 1000 microns, most optimally about 510microns, to maximize the device's functional longevity by increasing thecapillary tube's resistance to damage and minimizing its susceptibilityto hydrothermal erosion; (i) a capillary tube being composed of fusedsilica, preferably fluorinated fused silica, most preferably fluorinatedsynthetic fused silica, to optimally increase the resistance of thecapillary tube against damage due to back reflection of laser energy,back splatter degradation and hydrothermal erosion; (j) a capillary tubeoptimally having an eccentric channel, the greater wall thickness of thecapillary tube optimally being positioned at 180° opposite the beveled,distal end surface of the optical fiber, providing additional protectionagainst damage to the capillary tube from back reflection of laserenergy, back splatter degradation and hydrothermal erosion; (k) a distalend of the capillary tube, after having been closed by thermal fusion,being annealed by reducing the temperature of the capillary tube in aseries of timed steps to optimally reduce the presence of stresses inthe capillary tube; (l) a distal end of the capillary tube, after havingbeen closed by thermal fusion and annealed, being further tempered byrapidly reducing the temperature of the outer surface of the capillarytube to optimally increase the hardness of the outer surface of thecapillary tube; (m) a capillary tube optimally being close-fitted andnot fixedly attached over the distal end portion of the optical fiber,with a gap not exceeding 40 microns, creating a passageway for gassestrapped between the capillary tube and the distal end portion of theoptical fiber to expand, when heated by the emission of laser energy,without creating excessive pressure on the capillary tube and the distalend portion of the optical fiber; (n) a capillary tube being optimallyfixedly attached and close-fitted within an outer, hollow, protectivemetal sheath coated with, or preferably composed of, a material highlyreflective to the wavelengths of laser energy commonly used through sidefiring optical fiber devices, preferably a highly pure reflective metal,most preferably silver with a purity of about 99.5%, with a gap notexceeding 40 microns between the exterior of the capillary tube and theinner surface of the metal sheath, enabling the inner surface of thereflective metal sheath to reflect aberrant beams of laser energy fromimperfections in the beveled, distal end surface of the optical fiberand the interior surface of the capillary tube, back through thecapillary tube and out of the device, and enabling the outer surface ofthe reflective metal sheath to protect the capillary tube from backreflected laser energy, back splatter degradation and hydrothermalerosion; (o) a hollow metal sheath having a port for emission of laserenergy positioned at 180° opposite the beveled, distal end surface ofthe optical fiber and a distal end opening to optimally allow forwardlyemitted laser energy to escape, without overheating the distal end ofthe metal sheath and the capillary tube; (p) a hollow metal sheathhaving a wall thickness of about 300 microns, optimally bringing theoverall outside diameter of the side firing optical fiber device no morethan about 2.3 mm, enabling the side firing device to optimally passinto, move within and be withdrawn from the instrument channel ofcommonly available medical endoscopes; (q) a rigid, hollow shaftcomposed of one of: metal or plastic, preferably composed of medicalgrade stainless steel, with a wall thickness of about 300 microns,disposed over the optical fiber and extending from about the middle ofthe length of the capillary tube to about the proximal end of ahandpiece provided for ease of use by the operator, enabling the sidefiring optical fiber device to optimally resist rapid movement andvibration due to the equal and opposite forces exerted against the sidefiring device by the emission of laser energy, and enabling the sidefiring device to more easily being kept in place opposite the targettissue by the operator. (r) an optical fiber being fixedly attached tothe interior of the rigid, hollow shaft near the proximal end of thehollow shaft, to optimally allow movement of the beveled, distal endportion of the optical fiber within the capillary tube during handling,insertion into, during use and withdrawal of the side firing device fromthe working channel of an endoscope and optimally avoiding stress on theoptical fiber which could lead to premature failure of the device; (s) arigid, hollow shaft disposed over the optical fiber creating a channelenabling gasses trapped between the capillary tube and the beveled,distal end portion of the optical fiber to optimally expand, when heatedduring the emission of laser energy, preventing excessive pressure thatcan damage the capillary tube and the optical fiber; (t) a rigid, hollowmetal shaft having at least one vent near its proximal end, distal tothe point at which the optical fiber is fixedly attached to the interiorof the hollow rigid shaft, to allow gasses trapped between the capillarytube and the beveled, distal end surface of the optical fiber, whenheated by the emission of laser energy, to optimally escape into theatmosphere, without creating excessive pressure against the capillarytube and the distal end portion of the optical fiber; (u) a durable,lubricious outer sleeve of plastic, preferably composed of PEEK, with awall thickness of about 125 microns, fixedly attached to the metalshaft, enabling the side firing device to optimally pass into, be usedwithin and be withdrawn from the instrument channel of commonlyavailable endoscopes without scuffing and without excessive forces; (v)a durable, lubricious outer coating, with a wall thickness of at least0.1 microns, fixedly attached to the hollow shaft, enabling the sidefiring device to optimally pass into, be used within and be withdrawnfrom the instrument channel of commonly available endoscopes withoutscuffing and without excessive forces; and (w) a high temperatureoptically transparent epoxy, adhesive allowing the device to withstandthe elevated peak and average temperatures created at the end of theside firing device during use, and which does not significantly absorbthe wavelength of laser energy being used.
 10. The side firing opticalfiber device of claim 9, wherein the source of laser energy emits at awavelength of at one of: 300 to 400 nm, 400 to 1400 nm, 1500 to 1800 nm,1400 to 1500 nm, 1800 to 2300 nm.
 11. The side firing optical fiberdevice of claim 9, wherein the source of laser energy is one of: anexcimer laser emitting at a wavelength of one of: 308 and 351 nm, a KTPlaser emitting at a wavelength of 532 nm, a diode laser emitting at awavelength from 635 to 1100 nm, a diode laser emitting at a wavelengthof about 1470 nm, a diode laser emitting at a wavelength of about 1940nm, a Thulium:YAG laser emitting at a wavelength of 2000 nm and aCTH:YAG laser emitting at a wavelength of 2100 nm.
 12. A side firingoptical fiber device, comprised of a source of laser energy, an opticalfiber optically coupled to the source of laser energy, the optical fiberhaving a core of fused silica and an exterior cladding of fused silicadoped with fluorine in an amount sufficient to reduce its refractiveindex, the distal end of the optical fiber being beveled, and thebeveled, distal end of the optical fiber being encased by a distallyclosed-ended, fused silica capillary tube, providing an air interfaceopposite the beveled, distal end surface of the optical fiber necessaryfor total internal reflection of laser energy, and including at leastone of the following: (a) an optical fiber having an optimal corediameter of about 450 microns, able to efficiently transmit the highlevels of laser energy with wavelengths commonly used through sidefiring devices; (b) an optical fiber optimally having a cladding offluorinated, fused silica with a wall thickness of about 11 microns,with core-to-cladding ratio of about 1:1.05. (c) an optical fiberoptimally having an outer overjacket of undoped fused silica, preferablyundoped synthetic fused silica, with a wall thickness of about 65microns, with a combined core to cladding and overjacket ratio of about1:1.34, providing optimal protection to the thin, leading edge of thebeveled, distal end surface of the optical fiber; (d) an optical fiberhaving its distal end beveled at an angle of 35° to 45°, optimally at anangle of about 40° to 41° providing optimal total internal reflection oflaser energy at an angle of 80° to 82° laterally from the axis of theoptical fiber; (e) a beveled, distal end surface of the optical fiberhaving an optimal flatness, with a curvature across the surface of notmore than about 5 microns, most optimally not more than 1.3 microns tominimize laser energy transmission losses; (f) an optical fiber havingtaken a set while stored on a spool and, when unwound from the spool forfurther manufacture, using this set to optimally position the thinleading edge of the beveled, distal end surface of the optical fiberaway from contact with the inner surface of the distally closed-endedcapillary tube enclosing the beveled distal end portion of the opticalfiber; (g) a capillary tube being composed of fused silica, preferablyfluorinated fused silica, most preferably fluorinated synthetic fusedsilica, to optimally increase the resistance of the capillary tubeagainst damage due to back reflection of laser energy, back splatterdegradation and hydrothermal erosion; (h) a distal end of the capillarytube, after having been closed by thermal fusion, being annealed byreducing the temperature of the capillary tube in a series of timedsteps to optimally reduce the presence of stresses in the capillarytube; (i) a distal end of the capillary tube, after having been closedby thermal fusion and annealed, being further tempered by rapidlyreducing the temperature of the outer surface of the capillary tube tooptimally increase the hardness of the outer surface of the capillarytube; and (j) a capillary tube being optimally fixedly attached andclose-fitted within an outer, hollow, protective metal sheath composedof a material highly reflective to the wavelengths of laser energycommonly used through side firing optical fiber devices, with a gap notexceeding 40 microns, enabling the inner surface of the reflective metalsheath to reflect aberrant beams of laser energy back through thecapillary tube and out of the device.
 13. A side firing optical fiberdevice, comprised of a source of laser energy, an optical fiberoptically coupled to the source of laser energy, the optical fiberhaving a core of fused silica and an exterior cladding of fused silicadoped with a material, such as fluorine, to reduce its refractive index,the distal end of the optical fiber being beveled at an angle of 35° to45°, and the beveled, distal end of the optical fiber being encased by adistally closed-ended, fused silica capillary tube, providing an airinterface opposite the beveled, distal end surface of the optical fibernecessary for total internal reflection of laser energy, and includingat least one of the following: (a) an optical fiber having an optimal ODof about 600 microns, which is sufficiently small to enable as large aspossible wall thickness of a distally closed-ended capillary tube to beused to encase the beveled, distal end portion of the bared opticalfiber; (b) a capillary tube having a wall thickness of about 100 to 1000microns, most optimally about 510 microns, to maximize the device'sfunctional longevity by increasing the capillary tube's resistance todamage and minimizing its susceptibility to hydrothermal erosion; (c) acapillary tube being composed of fused silica, preferably fluorinatedfused silica, most preferably fluorinated synthetic fused silica, tooptimally increase the resistance of the capillary tube against damagedue to back reflection of laser energy, back splatter degradation andhydrothermal erosion; (d) a capillary tube optimally having an eccentricchannel, the greater wall thickness of the capillary tube optimallybeing positioned at 180° opposite the beveled, distal end surface of theoptical fiber, providing additional protection against damage to thecapillary tube from back reflection of laser energy, back splatterdegradation and hydrothermal erosion; (e) a distal end of the capillarytube, after having been closed by thermal fusion, being annealed byreducing the temperature of the capillary tube in a series of timedsteps to optimally reduce the presence of stresses in the capillarytube; (f) a distal end of the capillary tube, after having been closedby thermal fusion and annealed, being further tempered by rapidlyreducing the temperature of the outer surface of the capillary tube tooptimally increase the hardness of the outer surface of the capillarytube; (g) a capillary tube optimally being close-fitted and not fixedlyattached over the distal end portion of the optical fiber, with a gapnot exceeding 40 microns, creating a passageway for gasses trappedbetween the capillary tube and the distal end portion of the opticalfiber to expand, when heated by the emission of laser energy, withoutcreating excessive pressure on the capillary tube and the distal endportion of the optical fiber; (h) a hollow sheath disposed over thecapillary tube, being optimally composed of a material highly reflectiveto the wavelengths of laser energy commonly used through side firingoptical fiber devices, preferably a highly pure reflective metal, mostpreferably silver with a purity of about 99.5%, to provide optimalprotection to the capillary tube against damage from back reflectedlaser energy, back splatter degradation and hydrothermal erosion; (i) ahollow sheath having a port for emission of laser energy optimallypositioned at 180° opposite the beveled, distal end surface of theoptical fiber and a distal open end to optimally allow forwardly emittedlaser energy to escape, without overheating the distal end of the metalsheath and the capillary tube; (j) a rigid, hollow shaft comprised ofone of: metal or plastic, preferably composed of medical grade stainlesssteel, with a wall thickness of about 300 microns, disposed over theoptical fiber and extending from about the middle of the length of thecapillary tube to about the proximal end of a handpiece provided forease of use by the operator, enabling the side firing optical fiberdevice to optimally resist rapid movement and vibration due to the equaland opposite forces exerted against the side firing device by theemission of laser energy, and enabling the side firing device to moreeasily being kept in place opposite the target tissue by the operator;(k) an optical fiber being fixedly attached to the rigid hollow shaftnear the proximal end of the hollow shaft, to optimally allow movementof the optical fiber within the capillary tube during handling,insertion into, during use and withdrawal of the side firing device fromthe working channel of an endoscope and optimally reducing stresses onthe optical fiber; and (l) a rigid shaft disposed over the optical fibercreating a channel enabling gasses trapped between the capillary tubeand the beveled, distal end portion of the optical fiber to optimallyexpand, when heated during the emission of laser energy, and the rigidshaft having at least one vent near its proximal end to enable suchgasses to escape into the atmosphere, preventing excessive pressure thatcan damage the capillary tube and the optical fiber.
 14. A side firingoptical fiber device, comprised of a source of laser energy, an opticalfiber optically coupled to the source of laser energy, the optical fiberhaving a core of fused silica and an exterior cladding of fused silicadoped with as fluorine, in an amount sufficient to reduce its refractiveindex, the distal end of the optical fiber being beveled at an angle of35° to 42°, and the beveled, distal end of the optical fiber beingencased by a distally closed-ended, fused silica capillary tube,providing an air interface opposite the beveled, distal end surface ofthe optical fiber necessary for total internal reflection of laserenergy, comprised of at least one of: (a) a hollow shaft comprised ofone of: metal or plastic, disposed over the optical fiber, extendingfrom about the middle of the length of the capillary tube to about theproximal end of a handpiece provided for ease of use by the operator,the hollow shaft having a wall thickness of about 300 microns, enablingthe side firing optical fiber device to optimally resist rapid vibrationfrom the equal and opposite forces exerted on the side firing devicefrom the emission of laser energy, and enabling the side firing opticalfiber device to be more easily kept in position opposite the targettissue by the operator; (b) a durable, lubricious outer sleeve ofplastic, preferably composed of PEEK, with a wall thickness of about 125microns, fixedly attached to the hollow shaft, enabling the side firingdevice to optimally pass into, be used within and be withdrawn from theinstrument channel of commonly available endoscopes without scuffing andwithout excessive forces; and (c) a durable, lubricious outer coating,with a wall thickness of at least 0.1 microns, fixedly attached to thehollow shaft, enabling the side firing device to optimally pass into, beused within and be withdrawn from the instrument channel of commonlyavailable endoscopes without scuffing and without excessive forces. 15.A side firing optical fiber device capable of a consistently high rateof vaporization of tissue, extended longevity, high reliability andimproved handling, comprised of a source of laser energy, an opticalfiber optically coupled to the source of laser energy, the optical fiberhaving a core of fused silica with a diameter of about 450 microns and acladding of fluorine doped fused silica, preferably fluorine dopedsynthetic fused silica, with a wall thickness of about 11 microns, withan overjacket of undoped fused silica, preferably undoped syntheticfused silica, with a wall thickness of about 65 microns, the distal endof the optical fiber being beveled at an angle of 40° to 41°, and thedistal end portion of the optical fiber being disposed within a distallyclosed-ended capillary tube of fused silica, preferably of syntheticfused silica and most preferably of fluorine doped synthetic fusedsilica, with a wall thickness of about 510 microns, providing an airinterface opposite the beveled, distal end surface of the optical fibernecessary for total internal reflection of laser energy.
 16. The sidefiring optical fiber device of claim 15, wherein to increase itsfunctional longevity and reliability, a reflective metal sheath isdisposed over the capillary tube to protect the capillary tube fromdamage during use.
 17. The side firing optical fiber device of claim 15,wherein to eliminate the glass to air to glass interfaces that reducesthe overall laser energy transmission efficiency by about 7%, thecapillary tube is thermally fused to the optical fiber at one of:opposite the beveled, distal end surface of the optical fiber or alongthe line 180° opposite the bevel of the distal end surface of theoptical fiber, and further processed by one of: during the fusingprocess or after the fusing process, annealing the capillary tube andbared, distal end portion of the optical fiber by a series of timed,small reductions in temperature, while disposing a portion of theoptical fiber proximal to the capillary tube in an enclosure throughwhich a cooled fluid is circulated, to optimally reduce the presence ofstresses in the capillary tube and the optical fiber.
 18. The sidefiring optical fiber device of claim 15, wherein to resist vibrationfrom the equal and opposite forces exerted on the side firing device,the optical fiber is enclosed within a rigid, hollow shaft comprised ofone of: metal or plastic, preferably of medical grade stainless steelwith a wall thickness of about 300 microns, which shaft extends fromabout the middle of the length of the capillary tube to about theproximal end of a handpiece provided for ease of use by the operator.19. The side firing optical fiber device of claim 15, wherein thecapillary tube defines an eccentric channel providing a greater wallthickness of the capillary tube to be optimally disposed 180° oppositethe beveled, distal end surface of the optical fiber.